In zebrafish (Danio rerio), 6 distinct Na-K-ATPase (NKA) 1 subunit genes have been identified, and 4 of them, zATP1a1a.1, zATP1a1a.2, zATP1a1a.4, and zATP1a1a.5, are expressed in embryonic skin, where different types of ionocytes appear. The present study attempted to test a hypothesis of whether these NKA 1 paralogues are specifically expressed and function in respective ionocytes. Double fluorescence in situ hybridization analysis demonstrated the specific expression of zATP1a1a.1, zATP1a1a.2, and zATP1a1a.5 in NKA-rich (NaR) cells, Na⁺-Cl^- cotransporter (NCC)-expressing cells, and H⁺-ATPase-rich (HR) cells, respectively, based the colocalization of the 3 NKA 1 genes with marker genes of the respective ionocytes (epithelial Ca²⁺ channel in NaR cells; NCC in NCC cells; and H⁺-ATPase and Na⁺/H⁺ exchanger 3b in HR cells). The mRNA expression (by real-time PCR) of zATP1a1a.1, zATP1a1a.2, and zATP1a1a.5 were respectively upregulated by low-Ca²⁺, low-Cl^-, and low-Na⁺ fresh water, which had previously been reported to stimulate uptake functions of Ca²⁺, Cl^-, and Na⁺. However, zATP1a1a.4 was not colocalized with any of the 3 types of ionocytes, nor did its mRNA respond to the ambient ions examined. Taken together, zATP1a1a.1, zATP1a1a.2, and zATP1a1a.5 may provide driving force for Na⁺ coupled cotransporter activity specifically in NaR, NCC, and HR cells, respectively.